It is known that tertiary alkyl ethers, which are high octane blending components for motor fuels, can be prepared by reacting a primary alcohol with an olefin having a double bond on a tertiary carbon atom. For example, methanol reacts with isobutylene or isoamylene to form respectively methyl tert-butyl ether (MTBE) and tert-amyl methyl ether (TAME). Similar reactions are known which produce ethyl tert-butyl ether (ETBE) and tert-amyl ethyl ether (TAEE). Reference is had to U.S. Pat. Nos. 4,071,567; 3,979,461; 3,135,807; 3,846,088; among many others.
These ether reactions are so selective for tertiary olefins that they constitute a valid process for the removal from olefinic streams where there are encountered together with linear olefins. When producing such ethers however, it is desirable to remove the unreacted alcohol from the ether in the reaction effluent and recycle it to the ether reactor.
A variety of processes is known for the separation of alcohol from tertiary alkyl ether products. All of the known individual processes, however, fail to provide the flexibility of separating alcohol from a number of different ether products such as MTBE, ETBE, TAME and TAEE.
Accordingly it is an object of this invention to provide a process which will recover alcohol from a reaction mixture containing a tertiary alkyl ether.
Another object of this invention is to provide an improved arrangement of columns for extracting alcohol with water.
Another object of this invention is to provide a process which uses essentially identical process equipment to separate MTBE, TAME, ETBE or TAEE reaction products.
Still another object of this invention is to recover unreacted hydrocarbons from a tert-alkyl ether reaction product.